Only one breast sore before period? Maybe plugged duct?

Becky • Mom of 2 💕

Ok so this is the second month of this. A week or few days before my period starts I get pain in my right breast (outside closer to armpit). It mimics a plugged duct but there’s no lump. After my period it mostly goes away... although that spot always seems to be tender. Has anyone else experienced this before? Am I alone? My daughter is almost 6 months old and I exclusively pump. My right breast is also the main milk producer.